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Topic: Combining analog input (Read 2 times) previous topic - next topic

Grumpy_Mike

Yes that should do it.  :)

The transistor will get the pull up it needs through the multiplexer.

If it were me I would also put a 4K7 resistor from the  collector of the transistor to 5V but this is not essential. It is just it would make the transistor behave correctly even if it weren't switched through to the arduino.

DragoslaV

Alright! Thank you very much again for your help! :)

I will also put the 4K7 resistor between it. Also I was reading that only the digital pins has pull-up resistors? So its wise not to connect it on pin #19 but on #13 and below?

Grumpy_Mike

Quote
only the digital pins has pull-up resistors

No all the I/O pins on the processor have internal pull up resistors, even the analogue ones.
You can also put external pull up resistors on analogue inputs.

DragoslaV

Sweet  8) Thanks for the info! Time to get this working now :D

Cintax

#29
Mar 23, 2011, 03:34 am Last Edit: Mar 23, 2011, 03:43 am by Cintax Reason: 1
You can free up almost all the I/O you are using to drive the LED matrix with a MAX7219 or MAX7221 for each display.

http://www.maxim-ic.com/datasheet/index.mvp/id/1339

Also, keep in mind that you are not expressly using 12V here. Most charging systems actually sit around 14.5V to 15.5V. Motorcycles use a stator and rectifier which doesn't work in exactly the same as the alternator in your car to generate power. You will have voltage fluctuations at lower RPMs with charging (15.5V) occurring after 5000RPM.

Check your manual or measure voltage at different RPMs for exact values.

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